The invention relates to, in general, to medical x-ray imaging systems, and in particular to an apparatus for filtering an x-ray beam, having a filter which is adjustable from a parked position outside the x-ray beam or the x-ray beam path into a filtering position in the x-ray beam path.
The invention also relates to a medical x-ray system.
In a medical x-ray imaging system, a “quality” of a radiation, that is, an energy distribution of the radiological quanta, is determined not only by a voltage at an x-ray tube but also essentially by a downstream filtration. The filtration of the x-ray radiation is intended to substantially minimize low-energy quanta, which do not contribute substantially to an imaging and may lead only to an unnecessary radiation exposure. As a result of the filtration, a concentration point of or center of gravity of the energy distribution may shift toward higher values; the radiation is said to be “hardened”.
Particularly for cardiological examinations, copper pre-filters with various filter stages, that is with different absorption values, are necessary.
A filter changer with various filter stages is disclosed in German Patent Disclosure DE 198 32 973 A1 and in German Patent DE 42 29 319 C2.
An object is to disclose a filter apparatus which may enhance an operating safety for a patient to be examined using the filtered x-rays.
With respect to the apparatus referred to at the outset, this object is attained by a first sensor device for detecting the filter in the filter or filtering position and a second sensor device for detecting the filter in the parked position.
With the filter apparatus, one advantage is attained that incorrect positioning, for instance caused by failure of a structural part or a malfunction, can be ascertained substantially quickly and directly. Until now, such incorrect positioning could be ascertained only indirectly, from corresponding signs in the x-ray examination image or view found in an evaluation or observation of the x-ray image taken (reading the x-ray image). This may have caused unnecessary radiation exposure to the patient, because another x-ray image may have to be taken or a longer exposure time was necessary.
In a preferred feature, for each additional or further filter, a respective further first sensor device for detecting its filtering position and a further second sensor device for detecting its parked position may be present. Thus advantageously, filter apparatuses with a plurality of filter stages, in which a probability of incorrect or inaccurate positioning of individual filters is inevitably increased unless further precautions are taken, can be operated especially safely.
Preferably, the first and second sensor devices are embodied as photoelectric gates. Embodiments as electro-inductive, electro-capacitive or electro-resistive sensors are alternatively possible. The first and second sensor devices can also be embodied by a mechanical feeling or switch.
In another preferred feature, sensor signals are delivered or communicated to an evaluation device, which may generate a report if the filter, or one of the filters, is in neither its desired parked position nor its desired filtering position. With an evaluation device of this kind, preferably controlled electronically and/or by software, monitoring the respective positions can be automated, with a view to further enhancing safety.
The apparatus may be especially advantageous if a drive device or machine, such as a stepping motor, for moving the filter is present, as such, a corrective function of the drive device, and optionally of a control unit or device associated with the drive device as well, can also be monitored.
The filter apparatus is preferably embodied as a structural group or ensemble together with a multileaf diaphragm or collimator assembly, both of which are disposed in particular in a common housing.
For moving the filters, preferably present as a plurality of filters, in order to achieve various filter stages, an arm or handle can be separately present for each of the filters, and a first end of each arm may engage the applicably corresponding filter, while a respective second end of the arm can be subjected to a force generated by the drive device. As such, the x-ray apparatus is advantageously embodied such that as a function of a motion of the common drive device, one of the filters is either adjustable into the beam path by exertion of an adjusting force on the associated arm, or can be retrieved out of the beam path by exertion of a restoring or retrieving force on the arm.
In connection with this discussion, the term “arm” is understood to additionally mean or represent any mechanism for force transmission, for instance including a pusher, lever, rod linkage, or pivot joint.
In a preferred embodiment, a mechanism or device for holding, keeping or retaining each of the filters in a corresponding position in the beam path is present, in particular a detent mechanism or a magnetic coupling. As a result, it may be advantageously unnecessary for the drive device to generate a holding or retaining force for continuously holding the filter positioned in the beam path.
Preferably, there is a mechanism for holding and/or returning each of the filters in and/or into its position outside the beam path, in particular a restoring spring. Thus one further position is replicably defined in a simple way.
The mechanism for holding the filters in their respective positions in the beam path, in particular the spring or detent mechanism, are in particular dimensioned such that the restoring force of the restoring spring does not by itself suffice to allow a filter to leave its position, and that a filter can leave its position and return to its position outside the beam path when the restoring force generated by the drive device is exerted in addition.
In a preferred feature, the arms are mechanically encoded differently, specifically for both the adjusting motion and the retrieval motion. In particular, these arms are encoded mechanically differently such that as a function of predefined motions, different from one another, of the drive device, either one or more of the filters can be adjusted into the beam path, and that as a function of other predefined motions, also different from one another, of the drive device, either one or more of the filters can be retrieved from the beam path.
With increasing motion of the drive device in one direction, all the filters are preferably gradually adjustable into the beam path, and with increasing motion of the drive device in the opposite direction, all the filters can be retrieved gradually from the beam path.
In another preferred feature, the filters can be retrieved from the beam path in the same order in which they are adjusted into the beam path, and the adjustment and retrieval are done in particular in accordance with a first-in, first-out rule.
In addition, the filter apparatus is advantageously designed such that there is a drive device-driven slaving mechanism, which can be put into contact with two stops on each of the arms; an ON stop may be provided for subjecting the arm to the adjusting force, and an OFF stop may be provided for subjecting the arm to the restoring force. The slaving mechanism, which can also be designed as an intervention, has the advantage that the arms need not be coupled rigidly to the drive device, and so after the drive device has executed a first motion, the drive device can execute a second motion independently of the first motion.
In another special feature, for mechanically encoding the arms, the positions of the stops on different arms may be different from one another.
A further preferred feature provides a control unit for triggering the drive device; the control unit includes a memory device, in which codes of the arms that are different from one another and/or predefined motions of the drive device that are different from one another are or can be stored in memory. Preferably, motions that must be performed to realize different filter stages, that is, for introducing the filter or a combination of a plurality of filters into the beam path, are stored in memory. The stored motions can be read out electronically and are usable by the control unit for adjusting a desired filter stage or selected filter stages. Alternatively, the codes of the arms that are used by corresponding software program or programs can be stored, in order to calculate the particular motions required and trigger the drive device accordingly.
The control unit can also be embodied such that it substantially constantly records or keeps a log of which filters are located in the beam path at a given time and which ones are not. This embodiment has the advantage that the necessary motions of the drive device for adjusting a desired filter stage need not necessarily always be performed from a defined outset position of all the filters, such as all the filters not being in the beam path, but instead that under some circumstances, faster motion sequences can be employed from one filter stage to another. The required motion sequences in each case can be calculated by software, for instance. This embodiment produces the commands for driving the drive device.
The filters are, in particular, copper and/or aluminum filters or pre-filters and/or are distinguished or defined by different transmission values.
An additional scope also includes a medical x-ray system or machine, in particular for cardiology, having an x-ray source and having a filter apparatus, as described above, for filtering the x-ray beam emitted by the x-ray source.
The x-ray system is preferably designed such that an operation is interrupted if the evaluation device, which is in communication with the sensor devices, generates the report that the filter, or one of the filters, is in neither its parked position nor its filtering position.
Especially advantageously, a signal perceptible to an operator or user is output, in particular an optical or acoustical signal, if the evaluation device generates the report.